Objection 1. It would seem that the soul of Christ comprehended and comprehends the Word or Divine Essence. For Isidore says (De Summo Bono i, 3) that "the Trinity is known only to Itself and to the Man assumed." Therefore the Man assumed communicates with the Holy Trinity in that knowledge of Itself which is proper to the Trinity. Now this is the knowledge of comprehension. Therefore the soul of Christ comprehends the Divine Essence.
Objection 2. Further, to be united to God in personal being is greater than to be united by vision. But as Damascene says (De Fide Orth. iii, 6), "the whole Godhead in one Person is united to the human nature in Christ." Therefore much more is the whole Divine Nature seen by the soul of Christ; and hence it would seem that the soul of Christ comprehended the Divine Essence.
Objection 3. Further, what belongs by nature to the Son of God belongs by grace to the Son of Man, as Augustine says (De Trin. i, 13). But to comprehend the Divine Essence belongs by nature to the Son of God. Therefore it belongs by grace to the Son of Man; and thus it seems that the soul of Christ comprehended the Divine Essence by grace.
On the contrary, Augustine says (Qq. lxxxiii, qu. 14): "Whatsoever comprehends itself is finite to itself." But the Divine Essence is not finite with respect to the soul of Christ, since It infinitely exceeds it. Therefore the soul of Christ does not comprehend the Word.
I answer that, As is plain from 2, 1,6, the union of the two natures in the Person of Christ took place in such a way that the properties of both natures remained unconfused, i.e. "the uncreated remained uncreated, and the created remained within the limits of the creature," as Damascene says (De Fide Orth. iii, 3,4). Now it is impossible for any creature to comprehend the Divine Essence, as was shown in I, 12, 1,4,7, seeing that the infinite is not comprehended by the finite. And hence it must be said that the soul of Christ nowise comprehends the Divine Essence.
Reply to Objection 1. The Man assumed is reckoned with the Divine Trinity in the knowledge of Itself, not indeed as regards comprehension, but by reason of a certain most excellent knowledge above the rest of creatures.
Reply to Objection 2. Not even in the union by personal being does the human nature comprehend the Word of God or the Divine Nature, for although it was wholly united to the human nature in the one Person of the Son, yet the whole power of the Godhead was not circumscribed by the human nature. Hence Augustine says (Ep. ad Volusian. cxxxvii): "I would have you know that it is not the Christian doctrine that God was united to flesh in such a manner as to quit or lose the care of the world's government, neither did He narrow or reduce it when He transferred it to that little body." So likewise the soul of Christ sees the whole Essence of God, yet does not comprehend It; since it does not see It totally, i.e. not as perfectly as It is knowable, as was said in I, 12, 7.
Reply to Objection 3. This saying of Augustine is to be understood of the grace of union, by reason of which all that is said of the Son of God in His Divine Nature is also said of the Son of Man on account of the identity of suppositum. And in this way it may be said that the Son of Man is a comprehensor of the Divine Essence, not indeed by His soul, but in His Divine Nature; even as we may also say that the Son of Man is the Creator.
Source: Summa Theologica (New Advent)